The present invention relates to a zigzag arrangement of helical springs in devices for generating artificial reverberation.
Helical springs are used as a reverberation generating means in the most varied devices, from studio equipments of highest quality to electronic musical instruments, music amplifiers or electoacoustic installations, for improving the acoustic properties of rooms. In comparison with other possibilities of generating reverberation, helical springs are advantageous primarily because of their small dimensions, simplicity and cheapness.
Usually, such springs are stretched in straight lines so that, even though occupying a small volume, they extend over extensive distances. To reduce the constructional lengths of reverberation devices, an angular arrangement of helical springs has been provided.
Such an arrangement is known, for example, from U.S. Pat. No. 3,363,202. This patent discloses two helical springs arranged at an acute angle and changing into a meander-shaped flat spring in the vertex area of the angle. The two end portions of the flat springs remote from the helical springs are united at their point of intersection. At this point of intersection, a small helical spring is attached which, at its other end, is suspended from an elastic support.
This arrangement has the substantial disadvantage that the flat, meander-shaped, elastic elements differ from the helical spring not only in their external appearance, i.e. their shape, but also in the polar moment of inertia, per turn, and the elasticity, per turn. In consequence, and junction of a helical spring and a meander-shaped element constitutes a point of dicontinuity for the oscillations passing through the device, which discontinuity produces reflections reducing the quality of the artificial reverberation generated in the device and, therefore, undesirable.
Since the moment of inertial is proportional to the third power of the diameter of the helical spring, there results the further requirement that any deflection of any form must be designed so as to be effective as near to the spring axis as possible, or directly in the spring axis, because, otherwise, a too large moment of inertia would be implicated and an unacceptably strong junction area would be formed. The criterion for the design of such angular arrangements is thereby given. The smaller the junction area, the more frequently and universally such deflections per spring may be provided.
Another drawback of the arrangement in accordance with U.S. Pat. No. 3,368,202 is that, due to the flat, elastic elements at the deflection points, the effective length of the helical springs is considerably shortened and a relatively large space is necessary for the deflection.